1. Field of the Invention
The present invention relates generally to fastener devices and concrete construction and, in particular, to applicator tools and fastener devices used to fasten concrete reinforcement steel members together during concrete construction.
2. Description of the Related Art
Deformable metal fasteners called "hog rings" were originally developed in the 18th century to prevent hogs from rooting under fences that confined them. The hog ring device was inserted in a hog's nose and would cause discomfort and irritation if the animal tried to use its snout to dig. The hog ring was later used in a similar fashion on other livestock and also to connect wire fencing in agricultural applications.
In the early 1930s, automobile manufacturers began using hog rings to secure springs and wire in automotive seating. Today, hog rings are still widely used in the automotive industry for this purpose. Hog rings are also employed in the production of low cost upholstered furniture to attach upholstery material to a wire or rod support. Hog rings are similarly used as a fastening device in the bedding industry and in a variety of other industries.
A conventional hog ring fastener consists of a 15-gage wire having a length less than two inches, which is formed into a curved, C-shape with pointed, converging legs. The fastener is deformed when applied by a tool to close and cross the legs and form a loop around a work piece. Known hog ring fasteners are often assembled in strips or sticks and are dispensed in a tool one-at-a-time from a magazine. Conventional C-shaped hog ring fasteners are disclosed, for example, in U.S. Pat. Nos. 5,123,273 and 5,483,815.
Hog ring fasteners are generally designed with a structure or shape that prevents the opposed legs of the fastener from abutting and interfering with one another as the fastener is formed into a loop or ring. Such interference is undesirable because it can prevent the desired forming of the fastener into a loop and can cause jamming or wear and damage to a fastener application tool. The most common way to prevent interference between the legs of a hog ring is to provide the opposed legs with points that are offset or oppositely beveled, as shown, for example, in U.S. Pat. No. 3,628,230. Another known way to prevent interference between the legs of a hog ring is to provide an offset in the legs of the hog ring, as shown, for example, in U.S. Pat. No. 5,035,040.
Precast concrete, such as pipe, drainage structures, and building components (e.g., lintels, wall, floor, and roof panels) are normally reinforced with a latticework of rebar or wire mesh steel in single or multiple layers to enhance the strength of the concrete. The same is true of prestressed concrete, such as building components, bridge beams, and so forth. This is also the method used to reinforce virtually all cast-in-place concrete. For example, concrete highways are typically reinforced with a double mat of No. 5 rebar on six inch centers. When the concrete is being formed using reinforcement steel rebar or wire mesh, the rebar or wire mesh is typically laid out in a grid-like pattern or framework in a concrete form and secured together loosely using wire ties. The reinforcement steel is thus held in place temporarily by the wire ties while concrete is being poured around it. After the concrete sets, the reinforcement steel members are then permanently positioned within the concrete.
Most reinforcement steel members used in commercial concrete construction have been tied together in the same way for many years. The wire ties used to tie the reinforcement steel members together typically comprise very light gage, mild steel wire supplied on a belt-mounted reel. The wire is pulled from the belt-mounted reel, wrapped around the reinforcement steel members, pulled taut with side cutters or pliers, twisted, and cut. This conventional process of tying together reinforcement steel members is very labor intensive and, therefore, adds considerable labor costs to concrete construction jobs.
For example, reinforcement steel can be tied at concrete construction sites by skilled laborers at a rate of approximately 10 seconds per tie and a cost of $18 to $20 per hour using a reel of wire and pliers. Reinforcement steel can also be tied by semi-skilled laborers at a rate of approximately 25 seconds per tie and a cost of $6 to $8 per hour using a conventional loop or swivel process. The net cost of these two processes works out to be about the same.
Manufactured loop ties and hand swivels have also been used to secure reinforcement steel members together during concrete construction. For example, U.S. Pat. No. 3,331,179 discloses a grid of reinforcement steel members secured together, in part, using manufactured spacer rings at the intersection points of the reinforcement steel rods. The manufactured spacer rings are formed with a split 7 (see FIG. 3) for spreading the ring to mount the ring over the reinforcement steel rods. After the spread ring is mounted over the reinforcement steel rods, release of the spread ring results in reclosing of the ring upon the rods due to the elasticity of the material.
Such manufactured spacer rings are expensive to make because they require a relatively large amount of spring steel material for each ring to perform the intended function of spacing the grid away from the bottom surface of the concrete form, and also to provide the elasticity to reclose the ring upon the rods after the ring is spread to mount the ring over the rods. Moreover, such manufactured spacer rings are inefficient to use because they require a rather difficult and tedious process of spreading the rings during installation.
Hog rings and similar fasteners have not been previously used in the construction industry to secure reinforcement steel, such as rebar and welded heavy gage wire mesh, during concrete construction. Conventional hog rings are much too small for this purpose and have not heretofore been recognized as a possible solution to the high labor costs associated with concrete construction.
Moreover, prior art devices used to apply hog rings and similar fasteners in conventional applications have disadvantages that make the devices expensive and inefficient to manufacture and use. For example, U.S. Pat. Nos. 3,628,230, 5,035,040, and 5,123,273 each discloses a hand held, air-powered tool for applying hog rings for use in conventional applications. These prior art tools each utilize a complex mechanical linkage and jaw arrangement for deforming the hog rings, which are fed in one-at-a-time from a magazine. Another prior art applicator tool is disclosed in U.S. Pat. No. 5,483,815, which uses a rather complex and inefficient series of cams and jaws retained together by a neoprene O-ring. The disadvantages associated with each of these applicator tools would become even more apparent if the same designs were used to apply the larger fastener clips according to the present invention.